1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device with which a capacitor insulating film of a trench capacitor having a deep trench can be readily formed of a hafnium silicate film having a low impurity concentration and having an excellent step coverage property.
2. Description of Related Art
Along with scale down of semiconductor devices, the examination about application of a high dielectric constant film (a High-k film) to a material for each of a gate insulating film and a capacitor insulating film has been carried out. A lot of High-k films are made in the form of metallic oxides or silicate materials thereof. Of them, HfSiON which has a heat-resistance property as well as a High-k is a promising candidate for the material for each of the gate insulating film and the capacitor insulating film. High level control for a film thickness and a composition can be made by utilizing an atomic layer deposition (ALD) method of the various film depositing methods. This ALD method, for example, is described in Japanese Patent Laid-open No. 2004-165668. In any of the High-k materials, it has been found out that a leakage current is caused to flow through a film via trap levels provided by impurities contained in the film. Thus, it is very important to reduce a concentration of the impurities (such as carbon (C), hydrogen (H) and chlorine (Cl)) from a raw material. In spite of this situation, it is difficult to sufficiently remove the impurities through a treatment for changing a film property after deposition of the film. Therefore, it is important to sufficiently reduce the concentration of the impurities contained in the film at a stage of the film deposition.
On the other hand, for the purpose of promoting scale down, each of the recent capacitors ensures a sufficient surface area by adopting a three-dimensional structure such as a cylindrical shape or a deep trench (DT) shape. Thus, each of the recent capacitors maintains the data holding property. Therefore, it is necessary to realize a technique for forming an insulating film with excellent step coverage for the three-dimensional structure.
With the ALD method, since a gas phase reaction is suppressed as a temperature is lower, the excellent coverage property can be obtained. However, since the step coverage and the concentration of the impurities contained in the film show a trade-off relationship, it is difficult to find out the process condition under which the excellent step coverage property and reduction of the impurity concentration are met.